The path of a gun-launched projectile is at the mercy of gravity, air currents, muzzle accuracy, barrel wear, sighting accuracy, gun stability, projectile anomalies, charge uniformity, etc. As with a golfer who leans after a shot to encourage the ball to travel one way or the other, one would similarly like to influence the flight path of a bullet to overcome the above disturbances and to deliver the projectile to its intended target. The least expensive weapon has, for the last several centuries, been a bullet. But although bullets are themselves, very inexpensive, they are not always the most cost effective. That is, the real cost of a bullet kill includes the cost of all the ammunition used to achieve the kill plus the cost of delivery. There are expenses of the gun, the vehicle that carries the gun and the various support systems. There is also an implied cost in personnel. The most cost-effective weapons consider all aspects of cost.
Most bullets spin about their axis and are thereby spin stabilized. Equipping such a projectile with guidance vanes or other control devices would be useless unless said control devices could be activated only at such times and for an appropriate duration when they could impose the appropriate control force, and then be retracted when their affect would be inappropriate or counter to correcting the flight path. Obviously such operation would mean very rapid projection and retraction of the guiding aspects, i.e. a wide bandwidth control system. The need for a wide bandwidth control system may be avoided by de-spinning the section of the projectile that houses the control devices. The de-spun section may then be roll stabilized with respect to inertial space. In such a state, the control section moving axially through the air could activate control devices without subjecting them to the roll of the bullet.
The following terms are generally understood in the art and are used herein with the following definitions:
Missile refers to a self-propelled, unmanned aircraft. Propulsion may be supplied by a rocket, jet or other kind of motor.
Projectile refers to gun launched, ballistic weapons. They have been unpropelled in the past, but several projectiles under development or contemplated also have rocket boost.
Bullet is a small projectile, typically 3 inches or less diameter.
Gyro is an angular rate sensor.
Thus there is a particular need for an improved bullet capable of being delivered to an intended target in spite of the various influences that can set it off course. An object of this patent is to describe how a bullet in fight might correct an otherwise errant course when given the correcting information. Said information may come from outside the bullet, as in a command guidance system, or from and onboard auto-pilot. Another object of this invention is to achieve substantial cost reduction by making the bullet much more effective with only a modest increase in cost.
Accordingly, a bullet is described herein comprising: a spinning section adapted to rotate about an axis of flight; a control section rotatably connected to the spinning portion; a motor for de-spinning the control section relative to the axis of flight; a spoiler moveably connected to the control section; and an actuator connected between the control section and the spoiler for moving the spoiler between a withdrawn position and an extended position relative to the axis of flight. The bullet may further include a micro gyro attached to the control section and operable to generate a rotation signal responsive to the rotation of the control section about the axis of flight and a motor controller connected to the motor and having the rotation signal as an input and operable to control the motor in response to the rotation signal. In a further embodiment, the bullet is described as having a means for controlling the rotational position of the control section relative to the axis of fight so that a transverse force generated by the spoiler is oriented in a predetermined direction relative to the axis of flight, wherein the means for controlling the rotational position of the control section further comprises: a lens adapted for receiving an optical control signal; a detector disposed proximate the lens and operable to generate an electrical control signal responsive to the optical control signal; and an amplifier disposed on a flex circuit and connected to the detector for amplifying the electrical control signal, the flex circuit being bonded to the lens.